Nationwide, Bird, Lime, Spin, Goat and Skip have collectively deployed scooters in 33 cities. Outside of the U.S., you’ll find scooters from those companies in just three cities.

Bird and Lime are by no means the only companies working in this space, but they’re the two that have raised most the capital. Bird has raised $415 million in funding while Lime has raised $467 million. Bird and Lime are also the only two U.S.-based scooter companies that have gone international.

Over in the U.S., of course, the competitive landscape is an entirely different story. California is the main hot spot for scooters in the U.S., but they have also popped up in Texas, Washington D.C., North Carolina and other states throughout the country.

Unsurprisingly, regulation has proved to be an issue for many of these companies. In San Francisco, the Municipal Transportation Agency is currently reviewing permit applications from 12 electric scooter services — including ones from Lyft, Uber and Razor — looking to operate in the city. The permit process came as a result of Bird, Lime and Spin deploying their electric scooters without permission in the city in March. Fast forward to today and electric scooters are nowhere to be found on the streets of San Francisco.

The SFMTA initially said it expected to make a decision about which five, if any, companies would receive permits by the end of June. The SFMTA expects to finalize its recommendations and documentation “in the coming weeks,” the SFMTA wrote in a blog post last month. Once that’s done, the agency says it will work with companies to finalize and clarify the terms and conditions of the permit. The goal, according to the blog post, is to issue permits sometime in August.

As part of the 24-month pilot program, electric scooter companies selected to operate in the city will need to provide user education and insurance, share its detailed trip data with the city, have a privacy policy that protects user data, offer a low-income plan and operate in a to-be-approved service area. The city will allow no more than 2,500 electric scooters on the streets at any one time.

With the sheer volume of capital pouring into these companies, along with interest from ride-hailing giants Lyft and Uber, it’s clear these scooters are here to stay. Whether cities like them or not, scooters are going to roll up. It’s just a matter of when and how many.